2 links for the developers around here:

• Quick Lookup is an online dictionary of PHP,MySQL, Javascript and CSS commands and keywords. As of this moment, “55% ish of MySQL is done, JS is NOT finished yet” but it’s still useful if you haven’t got the PHP manual handy.
• Regular Expression Checker – regexes are an arcane science. Everyone needs all the help they can get when working with them! (via)

Later.. Here’s another AJAX powered regular expression checker via Matt.